It is known to use various fogging preventive techniques to obtain an image having reduced fogging (hereinafter referred to as "Dmin", Dmin being the lowest image density region of a final image) and a clean white background in the image, and it is typical to use a development inhibitor or a precursor thereof.
Examples of development inhibitors (including development inhibitor precursors) are described, for example, in Japanese Patent Application (OPI) Nos. 89034/75, 155837/79, 95539/85 and 144737/85 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application").
If sufficient fog inhibition is attained using the above development inhibitors or their precursors, the required development is also disadvantageously inhibited That is, if a strong development inhibitor is used or a large amount of a development inhibitor is used, generally the amount of developed silver is substantially reduced or the development rate is substantially lowered. In a color diffusion transfer process that uses dye-releasing redox compounds that can release dyes by silver development and a direct reversal emulsion, the maximum density (Dmax) is lowered and the development rate required to complete the image is lowered. The delay to complete an image is a serious disadvantage in the case of instant photography, wherein the ability to produce a picture quickly is very important.
The development of an effective development inhibitor free from such disadvantages has long been desired.